Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2021 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2022-026, 152 Pages, 2023/01

JAEA-Technology-2022-026.pdf:20.14MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2021. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data to create air dose rate distribution maps, and temporal changes of the air dose rates were analyzed. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Score maps to classify the importance of the measurement points were created for Fukushima Prefecture and the 80 km zone from the FDNPS, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. Monitoring data in coastal area performed owing to the comprehensive radiation monitoring plan until 2020 was summarized, and temporal changes in cesium-137 were analyzed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained in this project with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2021 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

The Data-base of the radiation monitoring in Fukushima based on the comprehensive radiation monitoring plan

Abe, Tomohisa; Ogiya, Takashi*; Shibata, Katsuya*; Hanawa, Tatsuaki*; Sanada, Yukihisa

JAEA-Data/Code 2020-004, 280 Pages, 2020/08

JAEA-Data-Code-2020-004.pdf:3.91MB

After the accidents at Fukushima Daiichi Nuclear Power Station (FDNPS), Japan Atomic Energy Agency has carried on survey for distribution situation of radiation materials under the direction of the Ministry of Education, Culture, Sports, Science and Technology (later the Nuclear Regulatory Agency) from June 2011 to FY2019. This report is mainly summarized as data-base of air dose rate, integrated dose and radionuclide concentration of some types of environmental sample (airborne dust, soil, pine needles) in the radiation monitoring in Fukushima Prefecture (20 km far from FDNPS). The results of radiation monitoring were analyzed for temporal change at each measurement site under the unification format. Furthermore, the effective half-life and the dispersion at each location and sample were evaluated based on these big data.

Application of the forest shielding factor to the maximum-likelihood expectation maximization method for airborne radiation monitoring

Sasaki, Miyuki; Sanada, Yukihisa; Yamamoto, Akio*

Radiation Protection Dosimetry, 184(3-4), p.400 - 404, 2019/10

https://doi.org/10.1093/rpd/ncz095

The maximum-likelihood expectation maximization (ML-EM) method is expected to improve the accuracy of airborne radiation monitoring using an unmanned aerial vehicle. The accuracy of the ML-EM method depends on various parameters, including detector efficiency, attenuation factor, and shielding factor. In this study, we evaluate the shielding factor of trees based on several field radiation measurements. From the actual measurement, the shielding factors were well correlated with the heights of the trees. The evaluated shielding factors were applied to the ML-EM method in conjunction with the measured data obtained from above the Fukushima forest. Compared with the conventional methods used for calculating the dose rate, the proposed method is found to be more reliable.

Evaluation of ecological half-life of dose rate based on airborne radiation monitoring following the Fukushima Dai-ichi Nuclear Power Plant accident

Sanada, Yukihisa; Urabe, Yoshimi*; Sasaki, Miyuki; Ochi, Kotaro; Torii, Tatsuo

Journal of Environmental Radioactivity, 192, p.417 - 425, 2018/12

https://doi.org/10.1016/j.jenvrad.2018.07.016

Study for estimation of snow depth by using DSM made by SfM method

Miyasaka, Satoshi*; Unome, Sota*; Tamura, Ayako*; Ito, Yoshiaki*; Ishizaki, Azusa; Sanada, Yukihisa

Nihon Rimoto Senshingu Gakkai Dai-63-Kai (Heisei-29-Nendo Shuki) Gakujutsu Koenkai Rombunshu (CD-ROM), p.81 - 84, 2017/11

Information of snow depth is important to improve the airborne radiation measurement in the winter. The snow depth is enable to estimate by the aerial photograph which is obtained at the same time with the radiation measurement before and after the snowfall. We attempted optimization parameters which used to make a Digital Surface Model (DSM) using Structure from Motion (SfM) method for estimation of the snow depth. As a result, to enable to measure precisely the snow depth was indicated. However, the estimated snow depth in the forest area was relatively not so accurate because fallen leaves and a tree move were prevented to measure DSM precisely.

Altitude control performance improvement via preview controller for unmanned airplane for radiation monitoring system

Sato, Masayuki*; Muraoka, Koji*; Hozumi, Koki*; Sanada, Yukihisa; Yamada, Tsutomu*; Torii, Tatsuo

Nihon Koku Uchu Gakkai Rombunshu (Internet), 65(2), p.54 - 63, 2017/02

https://doi.org/10.2322/jjsass.65.54

This paper is concerned with the design problem of preview altitude controller for Unmanned Airplane for Radiation Monitoring System (UARMS) to improve its control performance. UARMS has been developed for radiation monitoring around Fukushima Daiichi Nuclear Power Plant which spread radiation contaminant due to the huge tsunamis caused by the Great East Japan Earthquake. The monitoring area contains flat as well as mountain areas. The basic flight controller has been confirmed to have satisfactory performance with respect to altitude holding; however, the control performance for variable altitude commands is not sufficient for practical use in mountain areas. We therefore design preview altitude controller with only proportional gains by considering the practicality and the strong requirement of safety for UARMS. Control performance of the designed preview controller was evaluated by flight tests conducted around Fukushima Sky Park.

Determination of elemental composition of airborne dust and dust suspended in rain

Miyamoto, Yutaka; Saito, Yoko; Magara, Masaaki; Usuda, Shigekazu

Journal of Radioanalytical and Nuclear Chemistry, 255(3), p.553 - 557, 2003/03

https://doi.org/10.1023/A:1022548919533

To investigate the effect of weather on the composition of the dust and the possible origin of the dust, the elemental composition airborne dust was determined by INAA. The analyzed elements could be classified into 3 groups by the variation of concentration in the samples. The difference in concentration pattern may reflect the effect of rainfalls.

Deposition fractions of submicron aerosol particles in an air sampling pipeline

Matsui, Hiroshi

Earozoru Kenkyu, 11(4), p.337 - 348, 1996/00

http://ci.nii.ac.jp/naid/10002687424

no abstracts in English

Evaluation on collection efficiency of activated carbon fiber filter for radioactive hydrogen sulfide in air effluent monitoring

; Kajimoto, Yoichi; ; Endo, Akira; Ikezawa, Yoshio

Hoken Butsuri, 29, p.189 - 194, 1994/00

https://doi.org/10.5453/jhps.29.189

no abstracts in English

Advanced dust monitoring system applied to new TRU handling facility of JAERI

; ; ;

Proc. of Asia Congress on Radiation Protection, p.216 - 219, 1993/00

no abstracts in English